The present invention relates to a carbon/silicon carbide composite material, excellent in residence to wear, to be used for members for continuous casting or sliding members.
A carbon substrate is used for a member for continuous casting or a sliding member, because of its self-lubricating property and excellent residence to wear.
There is a limit to improvement in resistance to wear to be expected of the carbon substrate alone. For further improvement in the resistance to wear of the carbon substrate, a variety of surface treatment technologies have been proposed hitherto.
Japanese Laid-open Patent Publication No. Sho 62(1987)-270250 discloses means for converting a surface of the carbon substrate into a silicon carbide layer by the CVD (Chemical vapor deposition) method or the CVR (Chemical vapor reaction) method. However, the silicon carbide layer formed by the CVD method is disadvantageously liable to peel off, and the silicon carbide layer formed by the CVR method has a disadvantage of being lack of denseness. In addition, both the CVD method and the CVR method need large-scaled facilities. Accordingly, the both have not yet come to be commercially practical.
Japanese Laid-open Patent Publication No. Hei 8(1996)-12474 discloses means for converting a surface of carbon substrate into a silicon carbide containing carbon layer by a method of the surface of the carbon substrate being coated with slurry mixing resin and silicon powder and then being heat-treated at over 1,500xc2x0 C., for the purpose of improving the resistance to wear of a sliding seal member. However, since the silicon powder being gasified under high temperature to be allowed to react with carbon forms the silicon carbide, it is hard for silicon gas to penetrate into the inside of the carbon substrate. Because of this, it was infeasible to obtain the silicon carbide containing layer uniformly penetrating into the inside. The material thus formed cannot be used for applications such as members for continuous casting or sliding members, which need to allow for costs resulting from machining or wearing.
Japanese Laid-open Patent Publication No. Hei 7(1995)-144982 discloses means for converting a surface of the carbon substrate into a silicon carbide containing layer and also forming a dense surface layer formed of silicon, ceramic and carbon, to produce a two-layer structure by a method of the surface of the carbon substrate being coated with slurry mixing resin, silicon powder and ceramic and then being heat-coated at over 1,500xc2x0 C., for the purpose of improving oxidation resistance of a heat resisting member. However, since the surface layer is of thin, this material cannot be used for applications such as members for continuous casting or sliding members which need to allow for costs resulting from machining or wearing.
It is the object of the present invention to provide a carbon/silicon carbide composite material in which a deeply and uniformly penetrating silicon carbide containing carbon layer is formed as a first layer on a surface of a carbon substrate to produce a further improved wear resistance.
To accomplish the object, the inventors devoted themselves on the concerned study and discovered that when the slurry of silicon (Si) and boron carbide (B4C) was used, the silicon was surprisingly penetrated deep into the inside of the carbon substrate, so that a deeper and uniform silicon carbide containing carbon layer (it is hereinafter referred to as the SiC/C layer) was formed. Based on this discovery, the inventors have completed the present invention.
The present invention is directed to a carbon/silicon carbide composite material wherein a silicon carbide containing carbon layer which is formed by silicon and boron carbide being penetrated from a surface of a carbon substrate into the inside thereof to allow the silicon and carbon of the carbon substrate to react with each other so as to be converted into silicon carbide and in which the SiC is dispersed generally uniformly along a depth direction is formed as a first layer, the silicon carbide containing carbon layer having a thickness of not less than 1 mm. Also, the present invention is directed to a carbon/silicon carbide composite material wherein the SiC/C layer is formed on the surface of the carbon substrate as the first layer, and boron compound is mixed with silicon carbide in the layer.